1. Field of the Invention:
The present invention relates to a positioner which can easily set an output signal such that a controlled object is set to an arbitrary control condition corresponding to an input signal and its setting method.
2. Description of the Related Art:
Positioners have been used for controlling actuators such as diaphragm motors, cylinders and the like. The positioner controls a pressurized fluid in response to an input signal inputted as an electric signal, an air pressure signal or the like and sets a rotational angle of a rotary shaft of the diaphragm motor, a displacement position or the like of a piston of the cylinder to a given angle and position.
For example, in case the diaphragm motor which is controlled by this positioner is used for opening or closing a valve, a flow rate of a fluid which flows through the valve can be controlled in response to an input signal such as an electric signal, an air pressure signal or the like inputted to the positioner.
In the above flow rate control, the rotational angle of the rotary shaft of the diaphragm motor is not necessarily proportional to the flow rate of the fluid which passes through the valve. Conventionally, in setting the input signal inputted to the positioner and the flow rate of the fluid which passes through the valve to have a proportional relation, flow rate characteristics respectively corresponding to a large number of input signals are required to be measured and a conversion relation which makes the flow rate characteristics linear must be obtained. Accordingly, an operation for setting the conversion relation is complexed and such a setting operation takes a considerably long time and pushes up the cost.